Thermal alarm device



Dec. 12, 1950 D. M. PALMER 2,533,835

THERMAL ALARM DEVICE Filed March 17, 1950 INVENTOR.

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A TTUI'FNEY Patented Dec. 12, 1950 OFFICEf'l THERMAL ALARM Darren Delos M. Palmer, Toledo, Ohio Application March 1'), 1950, Serial No. 150,130

1 Claim.

This invention relates to alarm devices, but more particularly to fire alarms which are automatically set in operation in response to temperature conditions.

An object is to produce a simple and inexpensive fire alarm which will automatically operate in response to fire or high temperatures to sound an audible warning which will signal the presence of fire or unusual heat conditions.

Another object is to produce a new and improved fire alarm involving a bell or gong, the clapper of which is normally restrained by a thermally responsive member which in the presence of a predetermined temperature condition, will release the clapper which through power means, will automatically" operate to sound the signal.

A further object is to produce a simple, inexpensive and compact fire alarm device involving a bell or gong, the clapper of which is actuated by escapement mechanism when the clapper is released by a thermally responsive arm which normally directly restrains the clapper.

Alstill further object is to produce a fire alarm device of the above character which can be readily and conveniently adjusted to respond to different temperature conditions and which involves a spring motor for actuating the escapement mechanism for actuating the clapper, the device being self-contained for convenient mounting in the desired location.

Other objects and advantages reside in details of construction, arrangement and operation hereinafter described, and for purposes of illustration but not of limitation, an embodiment of the invention is shown on the accompanying drawings, in which Figure 1 is a plan view of the fire alarm device viewed from the rear side; and

Figure 2 is a side elevation of the alarm device with a portion of the gong broken away to show the operating mechanism.

The illustrated embodiment of the invention comprises a concave-convex bell or song It, to the center of which on the inner or concave side is l fixed a sheet metal bracket H which is secured by a bolt and nut assembly 62. As shown, the bracket has a flat portion I3 which abuts against the inner side of the gong and thence extends at substantially right angles as indicated at It and thence a bracket plate 55 extends upwardly at right angles to the portion 54. At, the upper end of the bracket plate It is an inwardly extending arm portion [5 which is integral with an upwardly extending supporting arm ijl en the outlid-102) 2 side of the gong it. A hole it is adapted to re-', ceive a screw It for suspending or mounting, the alarm device on a suitable support. The clapper for the gong is on the inside and comprises a bullet-nosed hammer 23 which is secured by a screw 2! to a relatively long clapper arm 22 which extends upwardly and terminates in a re; Versely curved end portion which is secured as by welding to an escapement pawl 23 which is pivoted by a pin 2 to the bracket plate 15. I It should be noted that the pivotal mounting of the escapement pawl 23 and clapper arm 22 is directly above the mid point of the clapper are which is indicated by the full and broken linees of the clapper arm and hammer in Figure 1. This arrangement facilitates the pendulum-like swinging movement of the clapper and allows more strokes to be put out by the spring motor.

The spring motor is generally indicated at 25 and includes an escapement wheel 25 with which the escapement pawl 23 cooperates. Detail description of the spring motor 25 is not considered necessary since the same is well-known in the art. Sufiice it tc say that it incorporates a spirally wound spring 2i which can be manually wound up or tightened by a suitable winder 28, a ratchet wheel 29 and pawl carried by the larger gear 3i preventing the normal unwinding I of the spring and the main gear 3i being connectedthrough a suitable chain of gears to the escapeme'nt wheel 2'5 which imparts the desired operative swinging movement of the clapper.

Secured by the screw 2% to the hammer 25 is a metallic strip 32 which extends laterally of the hammer and is adapted to be engaged by the hook end 33 of a bi-metallic thermostatic arm 34 to hold or restrain the clapper away from the gong ll) substantially as shown in Figure 1. The arm 34 is elongate and is suitably fixed to a flange portion 35 of a sheet metal arm 36 of a bell crank 31 which is pivoted on a pin 3% which is suitably connected to a flat cover plate 355 which is secured to the bracket plate Ed by spacers or posts 40 having end prongs clinched over the cover plate and bracket plate, thereby holding the cover plate in spaced relation to the bracket plate. It will be understood that in response to predetermined thermal conditions, the thermostatic bi-metallic strip 23 i will automatically swing to the broken line position shown in Figure 1, thereby to release the clapper and enable the latter to repeatedly hit against the gong due to the action of the escapement pawl and wheel actuated by the spring motor.

The other arm 4! of the bell crank 31 extends upwardly and has an outwardly extending flange 42' which serves as a handle or handhold to enable convenient adjustment of the bell crank. Pressed inwardly from the bell crank arm 4| is a rib or detent 42 which is adapted to seat positively in one or another of the depressions 42a in the bracket plate 39 thereby positively to retain the bell crank 31 in the position of adjustment. Directly above the series of depressions 42a is a scale 44 which is suitably calibrated and has at one end the letter H indicating the high temperature and at the opposite end the letter L indicating the low temperature. According to the position of the pointer 43 with respect to the scale 44, it will be understood that the thermostat will operate either at a relatively high or a relatively low temperature, or at some predetermined temperature. Manifestly, the user may adjust the bell crank 31 so that the alarm will be sounded when a pre-selected temperature is attained in the location where the device is placed. By reversing the position of the bi-metallic arm 34, the alarm may be used for extreme low temperature warning or signal, as, for example, in the event a freezing temperature is reached, so that when such low temperature 's reached, the arm 34 will automatically move to the broken line position shown in Figure 1 to release the clapper.

From the above description, it will be manifest that I have produced an exceedingly simple and inexpens ve alarm device which will efiic ently operate for the purpose intended and serveas an audible signal to warn, for example, the occupants of a, home of a fire in an attic and such-signal will continue for an adequate perind of time to arouse the occupants. The adjustment feature of the device enables the alarm to be used efiectively in a basement where the setting would be toward the L" indication. On the other hand, a difierent setting would be de* sirable in the summer time since higher temperatures are reached in the attic by radiation from the sun on the roof. As above indicated, by reversing the action of the lei-metallic thermostatic strip, the alarm can be used to advantage for a low temperature alarm and would thus be advantageous for fruitgrowers and farmers to warn of frost or freezing weather.

It is to be understood that numerous changes in details of construction, arrangement and operation may be effected without departing from the spirit of the invention especially as defined in the appended claim. 1

What I claim is:

An alarm device comprising a gong, a bracket carried by the gong, a clapper including an arm and hammer, a motor having escapement mechanism includ ng an escapement pawl pivoted to said bracket, a connection between said clapper arm .and bracket enabling actuation thereof upon operation of the motor and recurrent impact of the'hammer against the gong, a bi-metallic thermostatic arm normally holding said clapper arm ineffective by a loose hook connection and adapted to release same upon predetermined change in temperature condition a bell crank arm providing a rigid mounting for one end of said thermostatic arm and pivoted to said bracket, a pointer on said bell crank arm, and a dial for said pointer whereby adjustment of the pointer relative to the dial varies the pressure of the thermostatic arm aga nst the clapper arm and indicates the temperature at which the ther-' mostatic arm releases the clapper arm.

DELOS M. PALMER.

REFERENCES CITED Fllhe following references are of record in the file of this patent:

UNITED STATES PATENTS 

